An analytic model for the structure of the gravity current from the middle to the southern basin of the Caspian Sea

This study investigates the formation and dynamics of gravity currents in the Caspian Sea using analytical, numerical, and dynamic models. Focusing on the deep overflow from the middle to the southern basin—driven primarily by temperature-induced density differences—the research highlights how cold, dense waters from the northern basin sink in winter, fill the middle basin, and flow into the southern basin through the Absheron Strait. CTD data from UNESCO and simulations from the COHERENS ocean model support the analysis. The analytical model (based on Falcini and Salusti, 2015) is used to assess changes in vorticity and potential vorticity, incorporating entrainment and friction effects. A simplified dynamical model estimates the flushing time of deep waters in the southern basin to be 15–20 years, a timescale critical for ecosystem health and pollution impact, particularly from oil exploration. The study also finds that the deep overflow current interacts with existing oil and gas wells, suggesting a potential role in spreading deep-sea pollution.